The solubility of hydrogen in solid binary aluminum-lithium alloys

Abstract

The solubility of hydrogen in solid binary aluminum alloys with 1,2, and 3 wt pet lithium has been determined for the temperature range of 473 to 873 K and the pressure range of 26,700 to 113,300 Pa (0.26 to 1.12 atm), using an absorption/quench/desorption technique. The results fit the Van't Hoff isobar and Sieverts' isotherm and are given by log (S/S°)- log (p/p°) =-A/T/K +B whereS, S° are, respectively, the solubility and a standard value of solubility equal to 1 cm3 of diatomic hydrogen measured at 273 K and 101,325 Pa/100 g of metal;p, p° are, respectively, the pressure and a standard value of pressure equal to 101,325 Pa (1 atm). The values of the constantsA andB are Al-1 pet Li 473T/K 680:A = 358;B = 0.576 680T/K 873:A = 604;B = 0.620 Al-2 pet Li 473T/K 740:A = 273;B = 0.597 740T/K 873:A = 676;B = 0.767 Al-3 pet Li 523T/K770:A = 615;B = 1.272 770T/K 873:A = 830;B = 1.166 The solubility of hydrogen is one or two orders of magnitude greater in the alloys than in the pure metal and increases with lithium content. The results are consistent with the dissociative dissolution of a diatomic gas. The isobars are discontinuous at critical temperatures which lie within the a-phase field,i.e., 680, 740, and 770 K for Al-1 pet Li, Al-2 pet Li, and Al-3 pet Li, respectively, indicating a change in the character of the solution at lower temperatures due to an increase in the solute binding energy, which is attributed provisionally to an unidentified change in thea matrix.